When I find queen cups in my hive, I try and peer inside to see if there's anything in them, and as they have always appeared to be empty I then tear them down. How obvious would it be if they are not empty - e.g. if they have only an egg or very young larvae in them? I'm not convinced I would really be able to see egg/larvae in them until it was much further along. I've tried turning frames upside down so's I can see down into the cup more easily, but very wary of holding the frame at an angle to the sun in case of colapses!